The present invention relates to internal combustion engines. In particular, the present invention relates to air filters and filter elements used with internal combustion engines.
Internal combustion engines use air filters as a low cost means of providing clean combustion air to small utility engines. Many engines currently use air filters with panel type filter elements. Panel type filter elements can provide a large amount of filtration surface area in a narrow package size and are generally low cost due to the simplicity of the panel design.
In its basic form, a panel type filter element consists of two components. The first component is a pleat block, which is a length of filter media that is alternately folded to form a rectangular block. The pleat block is used to provide filtration of the incoming air before the air reaches the carburetor.
The second component is a seal bead, which is formed of an elastomeric material such as urethane foam or plastisol. The seal bead acts as a frame for the filter element, holds the pleat block, and provides a seal when the filter element is assembled into the air filter. Conventional air filter designs use a pair of opposed rib-like surfaces, one on the air filter base and the other on the air filter cover, to seal the air filter by xe2x80x9cpinchingxe2x80x9d the seal bead of the filter element between them. In addition, the filter element is retained in the air filter base by creating an interference fit between the outer perimeter of the seal bead and the inner perimeter of the outer wall of the air filter base. By adjusting the interference fit between the seal bead and the air filter base, the filter element can be retained in the air filter base without use of fasteners. Retention of the filter element in the air filter base is particularly useful for re-installing the air filter cover after servicing the filter element. The disadvantages of this method of retaining the filter element and sealing the air filter are the larger size and complex mold design for the air filter base created by having both the rib-like surface and the outer wall in the air filter base.
Typically, the pleat block is molded directly into the seal bead to create the complete filter element. In addition, a third component, a metal screen, is sometimes added to the filter element to provide rigidity and strength. The metal screen is typically also molded directly into the seal bead just in front of the pleat block.
Panel type filter elements are currently available in two basic designs. In the first design, the seal bead forms an internal area, which is generally rectangular in shape, and the internal area is completely filled by the pleat block. This type of filter element is placed in the air intake passage of the engine, typically just in front of the carburetor, where dirty intake air enters the filter element on one side and clean air exits on the other side and is provided to the carburetor.
In the second design, the seal bead forms two internal areas. The first internal area, as described above for the first design, is generally rectangular in shape and is completely filled by the pleat block. The second internal area formed by the seal bead is left open and does not contain a pleat block or any other filter material. The second internal area is generally used to seal previously cleaned air from the outside when the intake passageway of the engine must turn the air exiting the air filter 180xc2x0 to reach the carburetor.
In order to take advantage of the compact design of panel type filter elements, it is often necessary to place the filter element directly in front of the inlet to the carburetor. However, the carburetor will generally xe2x80x9cspit-backxe2x80x9d fuel due to the reverse flow pulse of air formed when the intake valve closes. This xe2x80x9cspit-backxe2x80x9d of fuel wets the filter media of the pleat block and causes it to plug prematurely, which reduces the effective life of the filter element. Filter elements that are kept dry have a tendency to self-clean for a period of time due to the reverse flow air pulses generated from intake valve closing. In addition, since emission regulations have been implemented, the oil mist leaving the engine crankcase via the crankcase breather hose must be ducted into the carburetor, where it will be burned in the engine instead of being released into the atmosphere as a pollutant. This oil mist from the crankcase breather hose can also wet the filter media of the pleat block and cause it to plug prematurely.
One way to minimize the wetting of the filter media of the pleat block is to provide a baffle, sometimes referred to as a xe2x80x9cspit-back cupxe2x80x9d, in front of the carburetor inlet and crankcase breather hose. The baffle blocks the fuel droplets flowing back out of the carburetor and the oil mist from the crankcase breather hose from reaching the filter element and provides a surface on which the fuel and oil can collect to form larger drops that will eventually flow back into the carburetor. The disadvantages of this design are the higher cost and larger size due to the extra parts of the baffle and a loss of engine power due to the air flow restriction imposed by baffle.
It would therefore be advantageous if a filter element could be designed that: (1) contained a seal bead that sealed the air filter and could be retained in the air filter base without requiring both a rib-like surface and an outer wall in the air filter base; and (2) that eliminated the need for a baffle. In particular, it would be advantageous if the filter element used the existing rib-like surface to both seal the air filter and retain the filter element within the air filter base, thereby eliminating the need for an extra outer wall in the air filter base, and contained a baffle integral to the filter element itself, thereby eliminating the need for the baffle in the engine.
The present inventors have discovered an air filter and air filter element design that eliminates the need for a baffle on the carburetor. The air filter element within the air filter contains an integral baffle which collects liquids that may be discharged from the carburetor and/or crankcase breather hose and protects the filter media of the pleat block in the filter element. Having the baffle as part of the filter element eliminates the need to have a baffle in the carburetor which reduces the cost and size of the carburetor and eliminates the loss of engine power that normally occurs due to the air flow restriction imposed by the baffle. In addition, the seal bead of the filter element contains a channel in which a sealing rib on the air filter base fits. This channel has an interference fit with the sealing rib on the air filter base, which allows the filter element to be retained during assembly without requiring an extra outer wall on the air filter base, thereby reducing the overall size of the air filter and simplifying the mold design for the air filter base. Finally, the air filter itself has an intake silencing chamber where external air is input and passed to the filter media of the filter element. The intake silencing chamber is sealed from outside air by the seal bead of the filter element thereby substantially reducing intake noise levels.
In particular, the present invention relates to a filter element for use in the air filter of an internal combustion engine that has a seal bead formed of an elastomeric material. The seal bead defines the outer circumference of the filter element and further defines a first area and a second area within the filter element. A filter media is molded into the seal bead within the first area of the filter element to filter incoming air. Finally, a baffle is located within the second area of the filter element to protect the filter media from wetting.
The present invention further relates to a filter element in which the seal bead that has a channel formed in one side and a surface formed on a second side, opposite the channel. The channel is used to retain the filter element during assembly and acts with the surface to seal the filter element within the air filter.
The present invention further relates to a filter element in which the seal bead further defines a third area within the filter element that creates a sealed flow path between an intake silencing chamber and the filter media to reduce intake noise levels.
The present invention further relates to an air filter for an internal combustion engine that has a base that includes a carburetor input formed in the base and a first sealing rib formed on the base. The air filter also has a cover that includes a second sealing rib formed on the cover. The second sealing rib has the same shape and size as the first sealing rib so that the sealing ribs are opposite each other when the base and cover are assembled. The air filter also has a filter element that has a seal bead formed of an elastomeric material. The seal bead defines the outer circumference of the filter element, which fits between the sealing ribs when the base and cover are assembled to seal the air filter, and further defines a first area and a second area within the filter element. A filter media is molded into the seal bead within the first area of the filter element to filter incoming air. Finally, a baffle is located within the second area of the filter, opposite the carburetor input, to protect the filter media from liquids from the carburetor input.
The present invention further relates to an air filter in which the seal bead of the filter element has a channel formed in one side that has an interference fit with the first sealing rib of the air filter base for retaining the filter element on the air filter base during assembly and sealing the filter element and the air filter base when the air filter is assembled. The seal bead also has a surface, opposite the channel, that is used to interface with the second sealing rib on the air filter cover to seal the filter element and the air filter cover when the air filter is assembled.
The present invention further relates to an air filter in which the intake silencing chamber is located to receive outside air before it is passed to the filter media and the seal bead further defines a third area within the filter element that creates a sealed flow path between an intake silencing chamber and the filter media to reduce intake noise levels.